Sespe Creek provides important spawning habitat for the endangered southern steelhead trout, which migrates from the Pacific Ocean, up the Santa Clara River and into Sespe Creek to spawn. The creek also supports one of the largest populations of endangered arroyo toads within a one-hundred miles radius. Its rich and relatively intact riparian habitat, which is rare in Southern California, supports the endangered southwestern willow flycatcher and least Bell's vireo and many songbirds.